This invention relates to the field of machinery rollers or drums and more particularly is related to the fastening of replaceable covers on rollers which are used as an anvil roller adjacent cutting rollers to provide a cutting surface for sheet material being transferred between the rollers. It is quite common in the industry of producing items from, for example, corrugated board material to utilize a rotary die cutter to produce the particular end product. The normal arrangement includes two adjacent rollers wherein one roller contains the cutting tools and an adjacent roller provides a contact surface for the blades which cut through the product material. In order to reduce general wear on the blades the exterior surface of the adjacent anvil roller is covered with a somewhat resilient or pliable cover material. However, after a significant amount of use the blades will wear or deteriorate the resilient cover to the point that is necessary to replace the cover.
It is very important to the efficiency of the overall manufacturing process to be able to replace the cover on the adjacent roller without having to disassemble the machinery and remove the drum. Consequently, a tubular type of covering may not be utilized, since it cannot be conveniently slipped over the end of the roller. Therefore, various means have been devised to removably attach a cover band or sheet around the drum. It is necessary that the roller cover be of a uniform thickness around the roller, so that, when the cutting blade from the cutting roller contacts the cover material on the adjacent anvil roller it will experience the same general resiliency in the cutting surface to insure proper cutting of the material passing between the rollers. Typically, roller covers comprise a plurality of separate circumferential cover bands which are affixed to the roller and are tightly adjacent each other.
In the prior art a transverse slot parallel to the roller axis has been incorporated in the surface of the roller into which respective flanges of each end of the roller cover material are inserted. However, it is necessary to have some type of metal support bar located within the slot below the respective ends of the cover material, so that the part of the cover material which extends over the slot will have adequate support and thickness equal to the rest of the surface of the drum. One type of prior art has utilized an L-shaped flange on each of the cover bands' transverse ends which must be placed within the slot prior to the placement of the support bar in the slot, because the support bar is anchored over a portion of each flange to secure the ends of the cover band to the roller. Since it is desirable to limit the number of transverse seams in the cover band to one and since the cover band is too stiff to bend back from over the slot, the support bar must be inserted or slid into the slot from the end of the roller, requiring the removal of all the cover bands in cases where only one needs to be removed.
Another prior approach uses a separate strip of the cover material placed over the support bar in the slot to eliminate the need to slide the support bar in from the end of the roller. However, this results in an undesirable double seam. The existence of multiple seams in the cover detracts from the general smooth continuous surface and increases potential problems where the cutting blades may become lodged within the seams. A related problem to the use of a separate strip of cover material is the undesirable slippage which commonly occurs in the strip. The movement of the adjacent rollers and their respective contact causes the strip portion to shift and move, adversely affecting the continuity of the surface necessary for a successful cutting operation.
Commonly, previous cover band latching devices tend to clamp the respective ends of the cover in place in the slot by the compressive force of a flanged support bar anchored to the roller by the fastening means. However, as a result of the forces exerted on the cover band associated with the cutting operation, the respective ends of the cover may transversely slip possibly causing an undesirable gap with the next adjacent cover band.